1. Field of the Invention
The present invention relates to a wafer processing apparatus, a wafer processing method, and a semiconductor substrate fabrication method and, more particularly, to a wafer processing apparatus for processing a wafer by dipping it into a processing solution, a wafer processing method, and a semiconductor substrate fabrication method.
2. Description of the Related Art
Cleaning processing is a typical example of wafer processing. One subject of wafer cleaning is to increase the speed. Japanese Patent Laid-Open No. 8-293478 has disclosed a wafer cleaning method capable of increasing the cleaning efficiency by supplying ultrasonic waves while rotating a wafer, and an apparatus for practicing this method.
The wafer cleaning method disclosed in Japanese Patent Laid-Open No. 8-293478 is based on the recognition that a wafer is most efficiently cleaned at the interface between a cleaning solution and ambient atmosphere. In the wafer cleaning method, therefore, particles inevitably attach to a wafer at the interface between the cleaning solution and ambient atmosphere.
In the wafer cleaning apparatus disclosed in Japanese Patent Laid-Open No. 8-293478, a cam mechanism for rotating a wafer is arranged immediately below the wafer, so a rotating force is not efficiently transmitted to the wafer. In the wafer cleaning apparatus, the transmission of ultrasonic waves is interrupted because the cam mechanism is laid out to completely shield the wafer from below. As a result, the strength of ultrasonic waves differs between the center and peripheral portion of the wafer, and the wafer cannot be uniformly processed. This nonuniformity cannot be improved by rotation of the wafer.
It is an object of the present invention to prevent contamination of a wafer by particles in various wafer processes including cleaning and etching.
It is another object of the present invention to make wafer processing uniform.
A wafer processing apparatus according to the present invention is a wafer processing apparatus for processing a wafer by dipping the wafer into a processing solution, characterized by comprising a processing bath having a depth that allows to completely dip the wafer into the processing solution, wafer rotating means for rotating one or a plurality of wafers held by a wafer holder by using a wafer rotating member which rotates about a shaft shifted from a portion immediately below a barycenter of the one or plurality of wafers, and ultrasonic generating means for generating ultrasonic waves in the processing bath.
In the wafer processing apparatus, only the wafer rotating member is preferably arranged as a member for transmitting a rotating force to the wafer below the one or plurality of wafers held by the wafer holder.
In the wafer processing apparatus, the wafer rotating member preferably comprises at least one rod member substantially parallel to the shaft, and the rod member preferably rotates about the shaft.
In the wafer processing apparatus, the rod member preferably has a diameter much smaller than a diameter of a cylinder virtually formed upon rotation of the rod member about the shaft.
In the wafer processing apparatus, the rod member preferably has a groove which engages with a peripheral portion of the wafer.
In the wafer processing apparatus, a section of the rod member taken along the shaft preferably has a substantially sine-wave shape.
In the wafer processing apparatus, a section of the rod member taken along the shaft preferably has a substantially full-wave rectifying shape.
In the wafer processing apparatus, the wafer rotating means preferably further comprises driving force generating means arranged outside the processing bath, and driving force transmission means for transmitting a driving force generated by the driving force generating means to the wafer rotating member and rotating the wafer rotating member.
The wafer processing apparatus preferably further comprises a dividing member for dividing an interior of the processing bath into a processing wafer side and a side of the driving force transmission means.
In the wafer processing apparatus, the driving force transmission means preferably transmits the driving force generated by the driving force generating means through a crank mechanism.
In the wafer processing apparatus, the processing bath preferably comprises a circulating mechanism having an overflow bath.
In the wafer processing apparatus, the circulating mechanism preferably comprises contamination reducing means for reducing contamination of the wafer by particles.
In the wafer processing apparatus, the contamination reducing means preferably comprises a filter.
In the wafer processing apparatus, the contamination reducing means preferably comprises means for adjusting flow of the processing solution in the processing bath.
In the wafer processing apparatus, the ultrasonic generating means preferably comprises an ultrasonic bath and an ultrasonic source, and the processing bath preferably receives ultrasonic waves through an ultrasonic transmitting medium set in the ultrasonic bath.
The wafer processing apparatus preferably further comprises driving means for changing a relative positional relationship between the ultrasonic source and a wafer to be processed.
In the wafer processing apparatus, the driving means preferably moves the ultrasonic source within the ultrasonic bath.
In the wafer processing apparatus, at least portions of constituent members of the processing bath and the wafer rotating means which may come into contact with the processing solution are preferably made of one material selected from the group consisting of quartz and plastic.
In the wafer processing apparatus, at least portions of constituent members of the processing bath and the wafer rotating means which may come into contact with the processing solution are preferably made of one material selected from the group consisting of a fluorine resin, vinyl chloride, polyethylene, polypropylene, polybutyleneterephthalate (PBT), and polyetheretherketone (PEEK).
A wafer processing method according to the present invention is a wafer processing method of processing a wafer while ultrasonic waves are supplied, characterized by comprising processing the wafer while entirely dipping the wafer into a processing solution and rotating the wafer.
A wafer processing method according to the present invention is a wafer processing method of processing a wafer while ultrasonic waves are supplied, characterized by comprising processing the wafer while entirely dipping the wafer into a processing solution, and rotating and vertically moving the wafer.
A wafer processing method according to the present invention is a wafer processing method of processing a wafer while ultrasonic waves are supplied, characterized by comprising processing the wafer while entirely dipping the wafer into a processing solution and changing a position of an ultrasonic source.
The wafer processing method according to the present invention is characterized in that the wafer is cleaned using a wafer cleaning solution as the processing solution.
The wafer processing method is suitable for a method of etching the wafer using a wafer etching solution as the processing solution.
The wafer processing method is suitable for a method of etching a porous silicon layer of a wafer having the porous silicon layer using a porous silicon etching solution as the processing solution.
The wafer processing method is suitable for a method of etching a porous silicon layer of a wafer having the porous silicon layer using, as the processing solution, any one of
(a) hydrofluoric acid,
(b) solution mixture prepared by adding at least one of alcohol and hydrogen peroxide to hydrofluoric acid,
(c) buffered hydrofluoric acid,
(d) solution mixture prepared by adding at least one of alcohol and hydrogen peroxide to buffered hydrofluoric acid, and
(e) solution mixture of hydrofluoric acid, nitric acid, and acetic acid.
A semiconductor substrate fabrication method according to the present invention is characterized by comprising the step of forming a non porous layer on a porous layer formed on a surface of a first substrate, the step of bonding a first substrate side of a prospective structure and a second substrate prepared separately to sandwich the non porous layer between the first substrate side and the second substrate, the removal step of removing the first substrate from the bonded structure to expose the porous layer on a second substrate side thereof, and the etching step of etching the porous layer while the second substrate side on which the porous layer is exposed is completely dipped into an etching solution, and ultrasonic waves are supplied, thereby exposing surface of the second substrate side, the etching step rotating the second substrate side.
A semiconductor substrate fabrication method according to the present invention is characterized by comprising the step of forming a non porous layer on a porous layer formed on a surface of a first substrate, the step of bonding a first substrate side of a prospective structure and a second substrate prepared separately to sandwich the non porous layer between the first substrate side and the second substrate, the removal step of removing the first substrate from the bonded structure to expose the porous layer on a second substrate side thereof, and the etching step of etching the porous layer while the second substrate side on which the porous layer is exposed is completely dipped into an etching solution, and ultrasonic waves are supplied, thereby exposing surface of the second substrate side, the etching step rotating and vertically moving the second substrate side.
A semiconductor substrate fabrication method according to the present invention is characterized by comprising the step of forming a non porous layer on a porous layer formed on a surface of a first substrate, the step of bonding a first substrate side of a prospective structure and a second substrate prepared separately to sandwich the non porous layer between the first substrate side and the second substrate, the removal step of removing the first substrate from the bonded structure to expose the porous layer on a second substrate side thereof, and the etching step of etching the porous layer while the second substrate side on which the porous layer is exposed is completely dipped into an etching solution, and ultrasonic waves are supplied, thereby exposing surface of the second substrate side, the etching step changing a position of an ultrasonic bath.
The etching solution used in the etching step is preferably any one of
(a) hydrofluoric acid,
(b) solution mixture prepared by adding at least one of alcohol and hydrogen peroxide to hydrofluoric acid,
(c) buffered hydrofluoric acid,
(d) solution mixture prepared by adding at least one of alcohol and hydrogen peroxide to buffered hydrofluoric acid, and
(e) solution mixture of hydrofluoric acid, nitric acid, and acetic acid.
The removal step preferably comprises exposing the porous layer by grinding, polishing, or etching the first substrate from a back surface.
The removal step preferably comprises separating the first substrate side and the second substrate side at a boundary of the porous layer.
The non porous layer is preferably a single-crystal silicon layer.
The non porous layer is preferably made up of a single-crystal silicon layer and a silicon oxide layer formed on the single-crystal silicon layer.
The non porous layer is preferably a compound semiconductor layer.
The second substrate is preferably a silicon substrate.
The second substrate is preferably a silicon substrate having a silicon oxide film formed on a surface to be bonded to the first substrate side.
The second substrate is preferably a light-transmitting substrate.
Further objects, features and advantages of the present invention will become apparent from the following detailed description of embodiments of the present invention with reference to the accompanying drawings.